The invention relates to an electromagnetic relay with a folding armature.
In such a relay (U.S. Pat. No. 4,260,973, the folding armature of the relay is held by a leaf spring at its support in engagements with the magnet yoke, wherein the leaf spring extend around the support in a form of a curl so as to be close to the support. The leaf spring is prestressed in such a way that it lifts the folding armature from the coil core when the relay winding is switched off and presses the switching contact fastened at the folding armature against a non-operating contact of the relay with a required contact pressure. In so doing, the folding armature is flipped with its support end around a support edge at the magnet yoke.
A disadvantage in this solution is that the contact of the folding armature at the support is only achieved when the center of rotation of the curl coincides with the support edge of the magnet yoke. However, as a result of the tolerances in the leaf spring curl area and the participating components, such as the armature plate and the magnet yoke, the ideal case of a force-free hinge-like contact is achieved, as well as a contact accompanied by pressing and friction, or no contact, i.e. a spacing between the armature plate and the armature bearing, in some cases accompanied by a distinct air gap. But both these cases are undesirable. The contact accompanied by pressing forces leads to a bearing friction, interference in the course of movement or possibly jamming. In the case of an air gap between the armature plate and the support edge, magnetic force is lost because of the increase in the magnetic resistance. This loss is expressed in increased response voltage values. Moreover, shaking and jarring shocks act in their entirety on the leaf spring curl which can be permanently deformed, which can impair the operational reliability of the relay and can lead to outage.